In the event of rehabilitation following any injury or simply in order to monitor and test an individual, it is important to ascertain the forces exerted by each of the legs when walking normally.
Apparatus is known which can be used to measure angular variations between the tibia and femur corresponding, in particular, to movements of flexion and extension when walking. In contrast, such apparatus provides no indication of the forces exerted by the foot.
In order to measure forces exerted by the foot, there are known systems which use a platform which rests on the floor and uses sensors. The platform is located along the path that is walked in order to obtain an image of the force exerted by a footstep. Nevertheless, it appears that such a solution is not satisfactory given the fact that the person has a natural tendency to pause before walking onto the platform so that the force which is exerted is not natural. This system can be duplicated for each leg. This system is not suitable for the measurement of several consecutive steps.
A proposal has also been made to equip endless belts in an attempt to measure the loads applied when an individual walks. This system involves fitting force meters between the base over which one side of the endless belt travels and the chassis. Such a solution has several drawbacks:
First the measurement cannot differentiate between the force exerted by each leg; this poses relatively few problems when analysing running motion because both feet practically never touch the ground simultaneously since contact is essentially one-footed but it is an important shortcoming when the individual is walking because both feet always touch the ground since contact is two-footed,
Second it is impossible to measure tangential forces.
Patent EP-A-0603115 and the Publication BIOMEDIZINISCHE TECHNIK, Volume 32, No. 10, October 1987 disclose solutions whereby the endless belt consists of two separate parts. In Patent EP-A-0603115, separation is transversal whereas in the Publication BIOMEDIZINISCHE TECHNIK, separation is longitudinal. This being so, in both cases the sensors are placed between the belt and the base, i.e. the part over which the belts travel. It therefore seems that these solutions cannot be used to measure tangential forces taking into account the friction of the belts on the base.
The invention aims to overcome these drawbacks in a simple, safe, effective and rational manner.
The problem which the invention aims to solve is to provide physiologists and orthopaedists with a solution capable of measuring vertical and horizontal forces, i.e. tangential forces of footsteps, especially for several successive steps by advantageously, but not exhaustively, differentiating between the forces exerted by the right leg and those exerted by the left leg.